In the hot pressing method of forming ceramics, the ceramics are under extremely high pressures and temperatures. The hot pressing apparatus inherently contains small amounts of air (i.e., oxygen), which oxygen combines with the carbon present to form carbonaceous gases, particularly carbon monoxide and carbon dioxide. These gases in turn formed undesirable carbides in the surface of the ceramic. The surface of the pressed ceramic had to be subjected to grinding to remove these carbides. This resulted in both a costly operation and loss of ceramic material.
It is known in forming ceramics to provide boron nitride (BN) powder on the ceramic as a release agent such as is disclosed in U.S. Pat. No. 4,252,768, granted Feb. 24, 1981 to Perkins et al.
Now there is provided by the present invention a paint which coats the ceramic preform and prevents undesirable carbides from forming on the hot pressed ceramic surface, and yet which paint may be readily removed so as to preserve substantially the entire ceramic.
It is therefore a principal object of the present invention to provide a new paint composition.
It is another principal object of the present invention to provide a paint and method as aforesaid in which the formation of undesirable carbides on the ceramic surface is eliminated.
It is still a further object of the present invention to minimize the loss of ceramic material in hot pressing.